Impact of the distance of light curing on the degree of conversion and microhardness of a composite resin.

OBJECTIVE: This study evaluated the impact of the distance between the light guide tip of the curing unit and material surface on the degree of conversion and Knoop microhardness of a composite resin. MATERIALS AND METHODS: Circular samples were carried out of a methacrylate micro-hybrid resin-based composite and light cured at 0, 2 and 4 mm distance. Monomer conversion rate was measured using a Fourier-transform Raman spectrometer and Knoop hardness number was obtained using a microhardness tester on the top and bottom surfaces. Data were statistically analyzed by analysis of variance and Tukey's test (α=0.05). RESULTS: Overall, the increase of curing distance reduced the microhardness (p≤0.05), but did not influence the carbon double bond conversion rate (p>0.05) of the composite resin tested; and the top surface showed better properties compared to the bottom (p≤0.05). CONCLUSIONS: The light curing at distance can reduce mechanical properties and could affect long-term durability of the composite restorations. Thus, the use of a curing device with high irradiance is recommended.

Mineral loss and color change of enamel after bleaching and staining solutions combination.

Pigments of food and beverages could affect dental bleaching efficacy. The aim of this investigation was to evaluate color change and mineral loss of tooth enamel as well as the influence of staining solutions normally used by adolescent patients undergoing home bleaching. Initial hardness and baseline color were measured on enamel blocks. Specimens were divided into five groups (n=5): G1 (control) specimens were kept in artificial saliva throughout the experiment (3 weeks); G2 enamel was exposed to 10% carbamide peroxide for 6 h daily, and after this period, the teeth were cleaned and stored in artificial saliva until the next bleaching session; and G3, G4, and G5 received the same treatments as G2, but after bleaching, they were stored for 1 h in cola soft drink, melted chocolate, or red wine, respectively. Mineral loss was obtained by the percentage of hardness reduction, and color change was determined by the difference between the data obtained before and after treatments. Data were subjected to analysis of variance and Fisher's test (α=0.05). G3 and G5 showed higher mineral loss (92.96 ± 5.50 and 94.46 ± 1.00, respectively) compared to the other groups (p ≤ 0.05). G5 showed high-color change (9.34 ± 2.90), whereas G1 presented lower color change (2.22 ± 0.44) (p ≤ 0.05). Acidic drinks cause mineral loss of the enamel, which could modify the surface and reduce staining resistance after bleaching.

Update on nonsurgical, ultraconservative approaches to treat effectively non-cavitated caries lesions in permanent teeth.

Dental caries on tooth surfaces is still a problem in many industrialized countries. For many years, dentistry was influenced by a mechanical approach characterized by the use of high-speed rotary cutting instruments, and dentists predominantly used surgical methods to address caries. This included radical removal of diseased portions of the tooth, along with material-driven geometric extensions to areas that were assumed to be caries-resistant. This concept of extension for prevention was introduced by G. V. Black and influenced dentists for more than 120 years. Recently, a new paradigm of operative conservatism, sometimes referred to as "minimally invasive dentistry," has gained popularity. This paradigm is designed to promote maximum preservation of healthy dental structures over a lifetime. The aim of this review is to discuss the efficacy of current nonsurgical treatments for non-cavitated caries lesions in permanent teeth. Based on results obtained from clinical trials, this review evaluates treatments such as consumption of CPP-ACP added gums, resin infiltration and fissure sealing. Although in a few cases an invasive approach is needed to arrest caries progression, the non-surgical approach generally provides potential benefits that include conserving structure by delaying intervention or minimizing the operative procedure. All current non-invasive methods are effective in treating non-cavitated caries lesions. The adoption of non-invasive approaches in the management of these lesions can preserve dental tissues, thus increasing tooth longevity.